Fun with Photos: What is this Boeing Truck Hauling?

The other day while going down I-405, which is just east of Seattle, I saw this very long Boeing truck being escorted by a Boeing van.

It is so long there is someone steering the rear wheels in the back. I have tried to do some research, asked a few people in aviation, put it out on Twitter, and talked to people at Boeing, but no one can tell me what it is hauling and what Boeing calls the truck.

So, time to use the power of my very smart blog readers (that is you!). What is the story behind this truck and what is it hauling?